Palatal Schwannoma: An Analysis of 45 Literature Reports ...Palatal Schwannoma: An Analysis of 45...

Palatal Schwannoma: An Analysis of 45Literature Reports and of an Illustrative CaseVivek Dokania1 Anagha Rajguru1 Vishwakarma Mayashankar2 Indranil Mukherjee3

Bhagyashree Jaipuria4 Devika Shere5

1Department of Ear, Nose, and Throat, Krishna Institute of MedicalSciences Deemed University, Karad, Maharashtra, India

2Department of Ear, Nose, and Throat, HBT Medical College and Dr RNCooper Municipal General Hospital, Juhu, Mumbai, Maharashtra, India

3Department of Ear, Nose, and Throat, Gouri Devi Institute of MedicalSciences and Hospital, Rajbandh, Durgapur, West Bengal, India

4Department of Ear, Nose, and Throat, Lokmanya Tilak MunicipalMedical College and Hospital, Sion, Mumbai, Maharashtra, India

5Department of Ear, Nose, and Throat, Rajiv Gandhi Medical College,Thane, Maharashtra, India

Int Arch Otorhinolaryngol 2019;23:360–370.

Address for correspondence Vivek Dokania, MBBS, MS, Departmentof Ear, Nose, and Throat, Krishna Institute of Medical Sciences,Deemed University, Karad 415110, Maharashtra, India(e-mail: [email protected]).

Keywords

► neurilemmoma► palate► schwannoma► S100

Abstract Introduction Schwannomas are benign tumors originating from differentiatedSchwann cells. Being the least common intraoral neoplasm of neural origin, it is rarelyseen in the palate. The literature lacks an extensive review of intraoral schwannomaconfined to the palate.Objective To review previously reported cases of palatal schwannoma along with anillustrative case, and to provide a better insight regarding clinicopathological andradiological features of this neural tumor in a rare intraoral site.Data Synthesis We present a case of palatal schwannoma in a 16-year-old female. Anadditional 45 cases were identified in 2 medical database searches (PubMed and GoogleScholar) published from the year 1985onwards, and from13 countries, in the 5 continents.Theages of the patients ranged from3 to84years old. Palatal schwannomashoweda slightpredilection to females, with a male/female ratio of � 1:1.81. Hard palate involvement isalmost twice greater than soft palate involvement. Surgical excision was employed inalmost all of the cases, and recurrence was reported only once.Conclusion Palatal schwannomas, although rare, have been reported both over thehard and the soft palate. They mostly present as a painless, firm, well-encapsulated,slow-growing solitary lesion over the lateral palatal aspect.Imaging can add to suspicion and can delineate a differential diagnosis, but thediagnosis is confirmed by pathological examination. Fine-needle aspiration cytology(FNAC) is almost always inconclusive. Immunohistochemistry can assist in confirming adiagnosis, but is more important to rule out close differentials. Complete surgicalexcision is the treatment of choice, and recurrence or malignant transformation areextremely rare.

Vivek Dokania's ORCID is https://orcid.org/0000-0002-6970-321X.

receivedMarch 22, 2019acceptedApril 13, 2019

DOI https://doi.org/10.1055/s-0039-1692635.ISSN 1809-9777.

Copyright © 2019 by Thieme RevinterPublicações Ltda, Rio de Janeiro, Brazil

Systematic ReviewTHIEME

360

Introduction

Schwannomaor neurilemmoma is a benign tumor of neuroec-todermal origin that is derived from Schwann cells of theneural sheath.1–3 In 1910, Verocay first described the micro-scopic features of this tumor under the term neurinoma.4 Theterm schwannomawas introduced byMasson in 1932.5 Later,in 1935, Stout3 used the term, neurilemmoma, and furtherdetailed its histopathology. In 1940, Tarlov described thetumor to be of fibroblastic origin and coined the term peri-neural fibroblastoma.6 About between 25 and 45% of allschwannomas are found in the head and neck region, andonly between 1 and 12% of them have an intraoral origin.7–9

However, the palatal location is rare. The present articlepresents a specific systematic review of the published litera-ture on palatal schwannomas, along with an illustrative case.

Review of the Literature

Case PresentationA 16-year-old female presented with a complaint of a pain-less swelling over the palatal region. She first noticed a smallnodule 2 months before, which was gradually increasing insize. She was otherwise healthy and did not report a historyof alcohol consumption or of smoking. No genetic or syn-dromic abnormalities were reported from her family. Herlaboratory reports were unremarkable. In the intraoralexamination, a solitary, nontender, firm swelling, �2.5 � 2 cm in dimension, was noted over the left soft palate.The tumor had a whitish-yellow appearance, and the over-lying mucosa was ulcerated (►Fig. 1). A computed tomo-graphy (CT) scan revealed a well-defined, hypodense, softtissue lesion measuring 27.8 � 21.6 � 18.2 mm involvingthe left side of the soft palate (►Fig. 2). With a probableclinical diagnosis of benign salivary gland tumor, the lesion

was completely excised and the defect was allowed to healby secondary intention. The histological examination of thelesion revealed a predominant presence of Antoni A areaswith spindle-shaped cells arranged in a palisading patternand central acellular areas representing Verocay bodies(►Figs. 3 and 4). Some areas also showed a hypocellularand less organized arrangement, as seen in the Antoni B type.The immunohistochemical (IHC) examination with S-100protein revealed intense positivity in the cells of the tumor(►Fig. 5). The tumor cells also showed positive expression ofSRY-related HMG-box 10 (SOX-10) protein (►Fig. 6). Basedon the clinical behavior, as well as on the histological and IHCfindings, the final diagnosis was of a benign schwannoma ofthe soft palate (conventional variant).

MethodologyA systematic review of the literature was performed inAugust 2018 on 2 different databases (PubMed and GoogleScholar). The database was searched for full-length articlesand abstracts using the following Medical Subject Headings(MeSH): palate, AND schwannoma, AND/OR neurilemoma,AND/OR neurilemmoma AND hard AND/OR soft palate, AND/

Fig. 1 Painless swelling over the left soft palate with ulceration of theoverlying mucosa.

Fig. 2 Computed tomography shows a hypodense, soft tissue lesioninvolving the soft palate on left side (red arrow).

Fig. 3 Section showing a spindle cell tumor and areas of collageni-zation (Hematoxylin and eosin staining; 100x).

International Archives of Otorhinolaryngology Vol. 23 No. 3/2019

Palatal Schwannoma Dokania et al. 361

OR intraoral MINUS tongue, vestibule and other intraoralanatomical locations. The search included synonymousterms and was confined to studies or reports in humans.The review included isolated case reports or articles with up

to 2 cases of palatal schwannomas published after 1984 inEnglish, German or Japanese. Articles containing > 2 cases ofpalatal schwannoma, or larger case series, were not included.Cases diagnosed as malignant schwannoma at the initialpresentation were not included. No age limits were applied.Information from the included articles was collected in apredesigned Microsoft Excel (Microsoft Corporation, Red-mond, WA, USA) spreadsheet.

Result

A total of 46 cases (45 published cases and an illustrativecase) of palatal schwannoma were included in the presentreview. From the included articles, clinical, histopathologi-cal, radiological, and treatment findings were charted(►Tables 1 and 2).10–54

Out of 46 compiled cases, 29 were female (64%), and 16were male (in 1 case, no gender was reported).45 The agesranged from 3 to 84 years old, with an average of 30.04 yearsold. The mean duration of the lesion from 38 reported caseswas of 25.63 months (range: 5days–20 years), while in theremaining 8 cases no information about the duration of thetumor could be retrieved (either the exact numerical dura-tion was not stated, or the lesion was incidentallydetected).10,17,33,38,39,44,46,47 Some articles reported theduration of onset in days, weeks or years. Therefore, theapproximate lesional age was converted and charted intomonths. The incorporated cases were reported from 13countries: India (n ¼ 15), USA (n ¼ 5), Brazil (n ¼ 5), Japan(n ¼ 4), Spain (n ¼ 3), Turkey (n ¼ 3), UK (n ¼ 2), Germany(n ¼ 2), Iran (n ¼ 2), Italy (n ¼ 2), Greece (n ¼ 1), Morocco(n ¼ 1), and Egypt (n ¼ 1) (►Fig. 7). Themajority of the caseshas been reported from India, indicating either a high pre-valence or a greater awareness about the disease in thatcountry.

The tumor involved the soft and the hard palate in 15(32.6%) and in 31 (67.4%) subjects, respectively. Among the15 soft palatal lesions, 8 involved the right side, 5 involvedthe left side, 1was in themidline, and no specific site over thesoft palate was mentioned in 1 case.22 Out of 31 hard palatallesions, 13were confined to the right hard palate, 11 involvedthe left side, 5 were in themidline, 1 involved the entire hardpalate, and no specific hard palatal location was reported in1 case.29

Most of the articlesmentioned thewidth and length of thelesion, but the depth dimension is rarely reported. Thelargest diameter/dimensions of the tumor ranged from5 cm to 1 cm, with an average of 2.4 cm (no informationabout the dimension of the lesion was reported in 2cases).13,17 When studying for an association between theduration of the lesion and lesion size, we found a weakpositive correlation (r ¼ 0.25). However, the correlation isstatistically insignificant (p ¼ 0.13) (►Fig. 8).

Symptoms were commented in 41 cases (89%). Theremaining 5 cases were incidentally detected or asympto-matic. Painless swelling/nodule was the most commonsymptom, present in 40 cases (87%). One case reporteddelayed pain over the tumor37 while in another patient,

Fig. 5 Section showing tumor cells expressing strong nuclear andcytoplasmic S-100.

Fig. 6 Section showing tumor cells expressing SRY-related HMG-box10 (SOX-10).

Fig. 4 Section showing proliferating fusiform cells arranged inpalisading pattern and areas of acellular eosinophilic regions repre-senting Verocay bodies (Hematoxylin and eosin staining; 200x).


Palatal Schwannoma Dokania et al.362

Table

1Re

view

ofprev

ious

lyrepo

rted

palatalsch

wan

nomas

Caseau

thors

Year

Age

/ge

nde

rCou

ntry

Lesion

duration

(mon

ths)

Clin

ical

symptoms

Lesion

size

(cm)

Site

Surgical

proce

dure

IHC

F/U

Recu

rren

ceMT

Variant

Yamashitaet

al10

1985

19/F

Japa

nNI

swellin

g1.5�

1.2

RSP

CEN

S-10

0þ

veNI

nono

cv

Jone

set

al11

1987

29/F

UK

24pa

inless

swellin

g2.5

RSP

CEN

NI

3years

nono

cv

Hieda

etal12

1987

44/M

Japa

n4

tumor

1.5�

1.2

RHP

WLE

&tumor

resected

enbloc

S-10

0þ

ve4months

nono

cv

Krollset

al13

1994

21/F

USA

12tumor,discomfort

during

eating

andtalking

NI

LHP

ExcisionBx

NI

3years

yes

noplx

Amiret

al14

2002

40/M

USA

3FB

sensation,d

ysph

agia,

garbledspee

ch5�

4EH

PWLE;seco

nda

ryintention

closu

reS-10

0þ

veNI

nono

cv

Rabb

elset

al15

2005

11/F

German

y3

painless

swellin

g2�

2RHP

WLE;co

llage

nclosure

S-10

0,Vim

entin

&NSE

þve

2years

nono

cv

Lópe

z-Carrich

eset

al16

2009

15/M

Spain

3sw

ellin

g1�

1.5

LHP

Incision

Bx-CEN

S-10

0þ

ve2years

nono

cv

Balig

aet

al17

2009

40/F

India

rece

ntly

painless

swellin

gNI

LSP

FNAC(IC)-WLE;co

llage

nclosu

reNI

10years

nono

cv

Murthyet

al18

2009

28/F

India

4sw

ellin

g,blee

ding

,with

tongu

epressu

re1.5�

1.5

LHP

Incision

Bx-CEN

NI

NI

nono

cv

Lolla

ret

al19

2010

33/M

USA

3en

largingmass

2�

2MHP

ShaveBx

-WLE

S-10

0&Vim

entin

þve

NI

nono

cv

Parikh

etal20

2010

64/F

India

36en

largingmass

2�

2MHP

CEN

NI

NI

nono

cv

Isild

aket

al21

2010

45/F

Turkey

180

enlargingmass

2�

2RHP

WLE

S-10

0þ

ve;Actin

-ve

NI

nono

cvwith

NFLA

Santos

etal22

2010

41/F

Brazil

60pa

inless

nodule

3�

1RHP

CEN

NI

NI

nono

cv

Santos

etal22

2010

53/F

Brazil

6pa

inless

swellin

g3�

3HP

CEN

S-10

0þ

veNI

nono

cv

Cha

wla

etal23

2011

9/M

UK

0.75

(3wee

ks)

painless

swellin

g,difficu

ltyin

eating

andsw

allowing

1�

1RSP

CEN

NI

1year

nono

cv

dosSa

ntos

etal24

2011

3/F

Brazil

6en

largingpa

inless

mass

1.6

RHP

CEN

S-10

0,Vim

entin,

EMA,

GFA

P,CD-57

&CD-56þ

ve,NF;

AE1

/AE3

,&Calpo

nin-v

e

1year

nono

plx

Dhu

par

etal25

2012

10/M

India

5sw

ellin

g,dy

sphag

ia,g

arbled

spee

ch,blee

ding

3�

2MHP

WLE;pa

latalsplinting

NI

NI

nono

cv

Han

dsch

elet

al26

2012

32/M

German

y24

enlargingno

dule

1�

2RHP

Incision

Bx-W

LE;prosthesis

placem

ent

S-10

0þv

e6months

nono

cv

Shetty

etal27

2012

70/F

India

24en

largingpa

inless

mass,

discom

fort

onmastication

2�

2RHP

FNAC(IC)-CEN

NI

8months

nono

cv

Prasan

naKu

mar

etal28

2012

18/m

India

22en

largingpa

inless

mass

3�

2.5

LHP

CEN

NI

NI

nono

cv

Kape

tana

kiset

al29

2012

21/F

Greec

e14

enlargingpa

inless

mass

1.5�

2SP

WLE

S-10

0þ

veNI

nono

plx

Rahp

eymaet

al30

2012

12/F

Iran

3en

largingpa

inless

mass

3RSP

Incision

Bx-CEN

;bu

ccinators

myo

muc

osal

flap

clos

ure

S-10

0þ

ve6months

nono

cv

Venka

tach

alaet

al31

2013

43/M

India

1sw

ellin

gan

ddy

spha

gia

2�

2RSP

CEN

S-10

0þ

veNI

nono

cv

Gainz

a-Cirau

qui

etal32

2013

35/F

Spain

60en

largingtumor

2�

1.5

MHP

FNAC(IC)-CEN

S-10

0þ

ve2years

nono

ancien

t

(Con

tinu

ed)



Table

1(Con

tinue

d)

Caseau

thors

Year

Age

/ge

nde

rCou

ntry

Lesion

duration

(mon

ths)

Clin

ical

symptoms

Lesion

size

(cm)

Site

Surgical

proce

dure

IHC

F/U

Recu

rren

ceMT

Variant

Chikh

aleet

al33

2013

42/F

India

IDID

2�

2LH

PCEN

NI

NI

nono

cv

Morad

zade

hKh

iavi

etal34

2014

21/M

Iran

2pa

inless

mass

2�

2MHP

Incision

Bx-CEN

S-10

0þ

ve6months

nono

cv

Aboh

etal35

2014

49/F

Italy

240

enlargingmass,

difficu

lty

withoral

hygien

e,ph

ona

tion

anddy

spnea

4�

3LH

PCEN

NI

1year

nono

cv

Parhar

etal36

2014

34/F

India

12en

largingpa

inless

mass

2�

1.5

RHP

Incision

Bx-CEN

NI

NI

nono

cv

Saho

oet

al37

2014

28/M

India

48en

largingmass,

pain

sinc

e3mon

ths

3LH

PFN

AC-W

LES-10

0þ

ve,S

MA-v

e10

mon

ths

nono

cv

Kudo

het

al38

2015

84/M

Japa

nID

ID3

LHP

Incision

Bx-partial

maxillec

t-om

y;split-thickn

essskin

graft

S-10

0þ

ve,

Ki-6

7þ

verate

1%29

mon

ths

nono

cv

Meu

ndie

tal39

2015

20/F

India

IDID

1�

3LH

PFN

AC(IC)-CEN

NI

2months

nono

cv

Tibb

etts

etal40

2015

11/F

USA

12en

largingmass

1RSP

WLE

NI

1mon

thno

nocv

Yaga

etal41

2015

28/M

India

12en

largingno

dule,

dysphag

ia4�

4RSP

FNAC-CEN

NI

NI

nono

cv

Karataset

al42

2015

36/F

Turkey

36en

largingmass

3�

5RHP

CEN

S-10

0&Vim

entinþ

ve18

mon

ths

nono

cv

Morga

net

al43

2015

16/F

India

12pa

inless

swellin

g2�

3RHP

FNAC(IC)-CEN

NI

NI

nono

cv

Siccaet

al44

2015

13/F

Italy

coup

leof

wee

ksrapidly

grow

ingmass

1.5

LSP

Incision

Bx-CEN

S-10

0þ

ve6months

nono

cv

Barhmie

tal45

2016

13/N

IMorocco

6pa

inless

swellin

g2

RSP

Incision

Bx-CEN

S-10

0þ

ve2years

nono

cv

Shie

tal46

2016

56/F

USA

IDID

1.6�

2LSP

Incision

Bx-CEN

S-10

0þ

ve;

AE1

/AE3

cytoke

ratin-ve

11da

ysno

nocv

Erog

luet

al47

2017

29/M

Turkey

IDID

2�

2LH

PEn

ucleated

(y-shap

edincision);

prim

aryclosu

reNI

18mon

ths

nono

cv

Poonjaet

al48

2017

30/F

India

8sw

ellin

g1�

1MHP

FNAC(IC)-CEN

S-10

0þ

ve1year

nono

cellu

lar

Vera-S

ireraet

al49

2017

26/F

Spain

>10

painless

swellin

g3�

2LSP

FNAC(IC)-CEN

S-10

0,CD-34,

EMA,

CD-117

&FV

III-RAþ

ve14

mon

ths

nono

ancien

t

Gue

iros

etal50

2017

26/M

Brazil

1/6

(5da

ys)

painless

nodule

2�

2RHP

Incision

Bx-CEN

NI

30mon

ths

nono

cv

Meloet

al51

2018

18/m

Brazil

36pa

inless

lesion

3.5�

3RHP

Incision

Bx-CEN

S-10

0þ

ve1year

nono

cv

Khaleleet

al52

2018

33/F

Egyp

t28

painless

swellin

g,discom

fort

inmastica

tion

2�

3RHP

FNAC(IC)-CEN

S-10

0þ

ve;NF-ve

NI

nono

cv

Murak

amie

tal53

2018

17/F

Japa

n12

swellin

g,ph

aryn

gealpa

inan

dredn

ess

2�

1.9

MSP

WLE;bu

ccinator

myo

muc

osal

flap

closure

S-10

0þ

ve6months

nono

cv

Presen

tcase

2016

16/F

India

2pa

inless

swellin

g2.5�

2LSP

CEN

S-10

0þ

ve&

SOX-10þ

ve1year

nono

cv

Abbreviations:þv

e,po

sitive

;Bx,biop

sy;C

EN,com

plete

excisionwithna

rrow

margin;

cv,con

ventiona

lvariant;E

HP,en

tire

hard

palate;E

MA,e

pithe

lialm

embran

ean

tigen

;F/U

,follow-updu

ration;

F,female;

FB,foreignbo

dy;F

NAC,fi

nene

edle

aspirationcytology

;GFA

P,glialfi

brillaryacidicprotein;H

P,ha

rdpa

late;IC,inc

onclusive;

ID,Inc

iden

tally

detected

;IHC,immun

ohistoch

emistry;

LHP,leftha

rdpa

late;L

SP,leftso

ftpa

late;M

,male;

MHP,midlin

eha

rdpa

late;m

o,mon

th/m

onths;

MSP,m

idlin

eso

ftpa

late;M

T,maligna

nttran

sformation;N

F,ne

urofilamen

t;NFLA,n

eurofibrom

a-lik

earea

s;NI,no

tinformed

;NSE

,neu

ronspec

ificen

olase;

plx,plex

iform

varian

t;RHP,right

hard

palate;R

SP,right

softpa

late;SMA,smoo

thmus

cle

actin;

SOX-10,

SRY-relatedHMG-box

10;SP,soft

palate;-ve,ne

gative

;WLE,widelocale

xcision;yr,year/yea

rs.



Table 2 Updated clinical profile of reported cases of palatal schwannomas

Clinical features of 46 patients with palatal schwannomas

Feature Dataa Number of cases amenable to analysis

Female 29 (64%) 45

Mean age at time of initial evaluation, years old 30.04 (range: 3–84) 46

Mean duration of lesion, months 25.63 (range: 5 days– 20 years) 38

Cases reported from India 15 (32.6%) 46

Hard palate involvement 31 (67.4%) 46

Soft palate involvement 15 (32.6%) 46

Mean size of lesion, centimeters 2.4 (range: 1–5) 44

Symptomatic cases 41 (89%) 46

Asymptomatic cases/ cases detected incidentally 5 (11%) 46

Symptoms at initial presentation

Painless swelling/nodule 40 (87%) 46

Painful lesion/ pharynx pain 2 (4.3%) 46

Dysphagia 5 (10.9%) 46

Dysphonia 3 (6.5%) 46

Dyspnea 1 (2.2%) 46

Difficulty in mastication 4 (8.7%) 46

Bleeding from tumor 2 (4.3%) 46

Foreign body sensation 1 (2.2%) 46

Pharyngeal erythema 1 (2.2%) 46

Signs at initial presentation

Tenderness over lesion 2 (4.3%) 46

Soft on palpation 4 (8.7%) 46

Ulcerated overlying mucosa 8 (17.4%) 46

Histological variant

Conventional 40 (87%) 46

Plexiform 3 (6.5%) 46

Ancient 2 (4.3%) 46

Cellular 1 (2.2%) 46

IHC positive staining 27b

S-100 27 (100%)

Vimentin 3 (11.1%)

EMA 2 (3.7%)

SOX-10 1 (3.7%)

NSE 1 (3.7%)

GFAP 1 (3.7%)

CD-56 & CD-57 1 (3.7%)

CD-34 & CD-117 1 (3.7%)

Surgical treatment 46

Enucleation/complete excision withnarrow margin/excision biopsy

33 (71.7%)

Wide margin excision 11 (24%)

Partial maxillectomy 1 (2.2%)

En bloc resection 1 (2.2%)

Prognosis 46

Recurrence 1 (2.2%)

Malignant transformation 0 (0%)

Abbreviations: EMA, epithelial membrane antigen; GFAP, glial fibrillary acidic protein; SOX-10, SRY-related HMG-box 10.aNumber (%) unless otherwise specified.bNumber of cases in which some form of immunohistochemistry staining was performed.



pharyngeal pain was present.53 Other symptoms werereported in the following frequency: dysphagia (n ¼ 5)14,23,25,31,41 dysphonia/garbled speech (n ¼ 3)14,25,35, dys-pnea (n ¼ 1) 35, difficult mastication (n ¼ 4) 13,23,27,52, occa-sional bleeding (n ¼ 2) 18,25, foreign body sensation (n ¼ 1)14, difficulty in oral hygiene (n ¼ 1)35 and pharyngeal red-ness (n ¼ 1) 53.

Clinically, most of the lesions were reported as nontenderand/or firm/hard. Tenderness was elicited only twice21,37,while soft swelling on palpation was reported in four cases18,38,43,44. Jones et al reported a cystic component in thelesion.11 Most of the lesions had a healthy overlying mucosawithout any obvious ulceration. Ulceration of the overlyingmucosa was noted in seven other cases apart from presentcase.13,23,30,31,34,37,44 The low frequency of ulcerationreflects a good encapsulation of this tumor.

Of the histological variant, the conventional subtypedominated and was reported in 40 cases (87%). It wasfollowed by plexiform-3,13,24,29 ancient-2,32,49 and cellularvariant- 1.48 Almost all of the cases with conventionalphenotype exhibited Verocay bodies and a predominanceof Antoni A areas over Antoni B areas. The additional pre-sence of acute and chronic inflammatory infiltrate,23 areas ofhyalinization, and thin blood vessels with/without throm-bus/fibrin,11,28,30,31,46 and areas containing epithelioid cellshave also been reported from cases with conventional phe-notypes.46 In one report, a note was made about the pre-dominance of neurofibroma-like areas.21

Various IHC stainingwere performed in 27 patients. S-100staining was employed in all of the 27 amenable cases, andshowed strong immunoreactivity in all of the employedcases. Other authors revealed varying degrees of positiveimmunoreactivity with different stains: vimentin,15,19,42

epithelial membrane antigen (EMA),24,49 SOX-10 (presentcase), neuron specific enolase (NSE),15 glial fibrillary acidicprotein (GFAP),24 CD-56 and CD-57,24 and CD-34 and CD-117.49 Immunonegative results were noted with the follow-ing stains: actin,21 neurofilament protein (NFP),24,52 smoothmuscle antigen,37 cytokeratin,46 AE1/AE3,24 and Calponin.24

Various imagingmodalities capable of revealing abnormalpalatalmorphologieswere performed on 36 patients, includ-ing simple X-ray scan in 1, panoramic radiography (ortho-pantomogram [OPG]) in 6, maxillary occlusal radiography in7, CT scan (with or without contrast) in 20, magneticresonance imaging (MRI) in 7, and positron emission tomo-graphy (PET) scan in 1 patient. The principal CT scan findingwas an isodense-hypodense soft tissue lesion without anybony erosion/resorption. Partial/complete bony erosion wasnoted in 6 instances.15,16,33,37,38,51 The lesion was seen

Fig. 7 Worldwide distribution of reported cases of palatal schwannomas.

Fig. 8 Relationship between lesion size and duration of lesion.



eroding into the rightmaxillary sinus through thefloor of thesinus in one case;15 while in another patient, the mass wasseen invading the nasal cavity through the palatal bone.38

Orthopantomogramand maxillary occlusal radiographyshowed mostly a radiolucent lesion, without any bonyalteration or periapical changes. In MRI exams, the massappeared hypo-to-isointense on T1-weighted images andhyperintense on T2-weighted images, in almost all of thecases. Small foci of central calcification were evident on MRIin one occasion.40

With the exception of two cases, all of the lesions weretreated with simple surgical removal, either with enuclea-tion, with wide local excision with a good margin, or with acomplete resection without incorporating a wide margin.The remaining two cases were treated by partial maxillect-omy,38 and by en bloc resection.12 The defect was eitherclosed primarily or was allowed to heal by secondary inten-tion. Otherwise, large defects were closed with some form ofprosthesis, splints, grafts or flaps. Reconstruction usingbuccinator myomucosal pedicle flap,30,53 split-thicknessskin graft,38 palatal splint,25 and collagen sheet have beenreported by various authors.15,17

Preoperative fine-needle aspiration cytology (FNAC) wasperformed in 10 cases, while incisional biopsy was per-formed in 13 cases. Fine-needle aspiration cytology wasinconclusive in almost all of the cases.

Postoperative follow-up was performed in 29 cases, andthe follow-up duration ranged from 11 days to a decade.Recurrence was noted only once,13 while none of theincluded cases reported malignant transformation.

Discussion

Schwannoma is synonymous with neurinoma, neurilem-moma, and perineural fibroblastoma.22 It arises from cranial,peripheral, or autonomic nerves that contain Schwann cells.It never arises from cranial nerves I and II, since they lackSchwann cells.16 Sensory nerve is more common, with rareinvolvement of motor nerve.54

About 25 to 45% of all schwannomas are found in the headand neck region, and only between 1 to 12% of them have anintraoral origin.7–9 However, the palatal location is rare. In areview of 52 cases of schwannomas of the head and neckregion, only 1 case of schwannoma over the hard palate wasreported.55 A review of the literature on oral, as well as onhead and neck schwannomas, showed varying results aboutthe gender predilection of the tumor.Williams et al showed amale predominance of the tumor; for Lucas et al, there was agreater predilection for females,56,57 while other authorsreported no gender predilection.58,59 Although reported inall age groups, schwannomas are more common in the 2nd

and 3rd decades of life.21

Intraoral and palatal schwannomas are mostly solitarylesions.34 Multiple nerve schwannomas require evaluationfor Von-Reklinghausen disease, while bilateral vestibularschwannomas raise suspicion for neurofibromatosis-II.30

The majority of palatal schwannomas have been reportedon the lateral aspect of the palate.

Based on its location, schwannomas have been classifiedeither as central (bone) or peripheral (soft tissue) type. Thetumor may arise centrally in the bone, may arise within thenutrient canal, or a soft tissue tumor may secondarily erodeinto the bony tissue.60 There are two clinical forms of oralschwannomas: the encapsulated form, surrounded by densefibrous connective tissue, and the pediculate/nonencapsu-lated form, in which the tumor is located just below themucous membrane.61

Although the etiology of schwannomas is unknown,trauma is considered to be an unclear etiological cause.2

There are various theories about its onset: 1) ectodermaltumor derived from Schwann cells; and 2) mesodermaltumor arising from the perineurium.38

Most of the cases are asymptomatic, while most of thelesions are slow-growing. A sudden increase in size may bedue to internal hemorrhage.16 The clinical presentationdepends upon the site of the tumor, the size of the tumor,and upon the anatomy of the affected nerve.32

There are four major histological types of schwannoma:conventional, plexiform, cellular, and ancient variant.According to Erlandson, schwannomas are classified intoseven subtypes: conventional, cellular, plexiform, cranialnerve, melanotic, ancient, and granular cell schwanno-mas.62 However, they have mainly two distinct histologicalpatterns: Antoni types A and B. Antoni patterns were firstdescribed by Prof. Nils Ragnar Eugene Antoni. Antoni Aareas consist of a hypercellular proliferation of fusiformcells, often arranged in a palisading pattern around acentral acellular eosinophilic area known as Verocaybodies, while Antoni B areas are hypocellular and lessorganized.

The conventional variant consistsmostly of Antoni A areasand Verocay bodies, with the occasional presence of Antoni Bareas. The additional presence of acute/chronic inflamma-tory infiltrate, areas of hyalinization, and thin vessels con-taining thrombin are noted in the conventional variant.22

The cellular variant is characterized by a marked increase incellularity, with a compact arrangement of spindle cells infascicles, variable nuclear hyperchromasia and pleomorph-ism, lack of Verocay bodies, and a predominance of Antoni Aareas.48,64 The cellular variant, due to the increased mitoticactivity and to the high potential for body destruction, isoften confused with sarcoma.65

The ancient variant is characterized by degenerativechanges, such as calcification, mild pleomorphism andbizarre nuclei, microcyst formation, dilated vessels, andhemorrhagic phenomena. Some authors believe that theabsence of symptoms and the long history of the lesion arethe probable cause of transformation into an ancient var-iant.32 The plexiform type consists of both Antoni A and Bregions with prominent Verocay bodies, like the conven-tional variant; however, the Schwann cells show a nodulararrangement with capsular delineation.24

Immunohistochemistry is important to distinguishschwannoma from other close differentials, and can aidin its diagnosis; however, it is not mandatory to confirmthe diagnosis. S-100 is undoubtedly the first



immunostaining that comes into mind when dealing withsuspected peripheral nerve tumors. Both schwannomasand neurofibromas show moderate to strong reactivity toS-100. However, S-100 has low specificity for diagnosingperipheral nerve cell tumors. One study has found Sox-10to be more sensitive and specific than S-100 for peripheralnerve tumors.66 Diffuse staining with CD-34 is seen inneurofibromas, while schwannomas only occasionallyshow some focal staining in noncellular (Antoni-B) areas.Calretinin staining is found to be highly specific forschwannoma and useful in differentiating it from neurofi-broma.67,68 Intensive staining with CD-57 is noted intraumatic neuromas.69 Schwannomas also stain positivewith Leu-7antigen, GFAP, and vimentin.18 The presence ofaxons in palisaded encapsulated neuroma (PEN) and,therefore, positive staining with NFP, distinguishes itfrom schwannomas.70 Staining with AE1/AE3 and withcalponin can help rule out salivary gland tumors.24

The major differentials are benign salivary glandtumors, benign peripheral nerve tumors (neurofibroma,traumatic neuroma, and PEN), other benign mesenchymaltumors (lipoma and hemangiomas), and odontogenictumors. Salivary gland tumors are the most commondifferential in our review, and were considered in 25 cases(54.3%).

Imaging modalities such as CT and MRI are useful duringthe initial workup to know the extent of the tumor, todelineate any bony erosion, to identify the nerve of origin,and to narrow the differentials.14,16,19,21 Yamazaki et alreported a case of a rapid growing lesion which was foundinMRI to be originating from themental nerve; therefore, theimaging exam assisted in the preoperative diagnosis of aperipheral nerve tumor that was otherwise considered amalignant lesion.71 Schwannomas mostly appear iso- tohypointense on T1-weighted MRI images and hyperintenseon T2-weighed MRI images. Computed tomography scansgenerally show awell-circumscribed, soft tissue lesionwith-out any bony erosion. However, schwannomas can occasion-ally cause pressure erosion of the bone.42,72 The proportionof Antoni-A and B areas has been reported to have a sig-nificant influence on the imaging findings. Gomez-Brouchetet al reported that vestibular schwannomas with a homo-geneous appearance on MRI were predominantly made ofAntoni-A tissues, while those with heterogeneous/cysticfeatures were predominantly composed of Antoni-B/mixedtissues.73

The therapy of choice consists of complete surgicalremoval. Schwannomas do not recur if they are completelyremoved. Only one case of benign palatal schwannoma hasbeen found to recur after excision.13 Malignant transforma-tion of head and neck schwannomas are exceedingly unu-sual, although it has been reported.74,75

Final Comments

There is barely any paper in the literature focusing exten-sively on palatal schwannomas, and tackling this benigntumor as an individual entity. Despite divergent inferences

from different articles, the following conclusions can bedrawn:

• Predominance in females, and involvement of the hardpalate is twice the involvement of the soft palate.

• Although reported in all age groups, schwannomas com-monly present during the 2nd or 3rd decades of life.

• Slow-growing tumor with amean lesion duration of 25.63months.

• Mostly present on the lateral aspect of the palate, withoccasional reports of midpalatal or panpalatal lesions.

• Almost always a solitary tumor, presenting as a painless,nontender, and firm swelling.

• The conventional variant is themost common histologicalphenotype.

• Imaging can add to suspicion and can delineate a differ-ential diagnosis, but the diagnosis is confirmed by patho-logical examination.

• Benign tumor of the salivary gland is the most commonclinical differential.

• Fine-needle aspiration cytology is mostly inconclusive.Immunohistochemistry can assist in confirming a diag-nosis, but is more helpful to rule out close differentials.

• Complete surgical removal is the treatment of choice.• Recurrence and malignant transformation are extremely

rare.

Conflicts of InterestsThe authors have no conflicts of interests to declare.

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